The present invention relates to devices and methods for the stocking/buffering of substrate and substrate carriers and particularly to stocking/buffering using a robot arm.
A semiconductor fabrication line performs various processing steps to wafer substrates to produce integrated circuits. Present fab systems use reticle or full wafer masks which are stored in standard mechanical interface (SMIF) pods, front opening unified pods (FOUPs), or stocked as bare masks. Wafer sizes vary depending on the semiconductor process; typical maximum sizes are 200 mm and 300 mm in diameter. Wafers can be stored in SMIF pods or FOUPs, which hold as many as 25 substrates.
Intermediate term stocking and short term buffering of substrate carriers is needed to supply the articles to the manufacturing steps as needed. To address the high throughput demands of many manufacturing environments a stocking/buffering system is needed to store carriers in quantity and transfer it via an automated method. The system is either placed in a stand-alone mode where its purpose is to feed material to the Fab itself or in a local mode where it feeds a local tool or tool cluster.
Presently, the main design technique in building these systems automation components is the use of Cartesian slide systems configured in such a way as to achieve the desired motion profile through a plurality of degrees of freedom, usually 3 or 4. The automation components are a combination of linear positioning stages and other motion systems.
One of the major problems of this method has been the automation component itself. Usually being an aggregation of several linear slides, the reliability and serviceability of such systems have been consistently poor. Linear slide systems are subject to alignment problems, which can cause binding and malfunction resulting in a low mean-time-between-failure performance. Also since this is not a true unified automated solution, the design, assembly, and programming time is greatly increased.
Another method of automation utilized is a selective or single compliant assembly robot arm (SCARA) robot mounted on an extra vertical axis of motion to achieve a specific Z height. Although this method is much more reliable than the Cartesian system, the SCARA robot needs a very large footprint to negotiate the product through. This in many cases, results in a system that is unacceptable in size to end users where applications are space critical.
The prior art stocking systems do not have the capability of selecting a carrier from a stocking area and transferring it directly to front end automation with multiple load ports.
A need exists for a method and apparatus for stocking substrate carriers that is small in footprint, highly reliable, and easy to service.
A new robotic storage system utilizes an invert mounted 6-axis articulated robot arm to transport objects such as FOUPs or SMIF pods between a storage location and an I/O load port. A seventh degree of freedom is provided by an end-effector to accomplish motion within a small space. FOUPs and SMIF pods are stored in a high density arrangement on shelves within a storage area. Each storage location within the storage area has a presence/absence detection sensor.
The present system provides in a storage buffer system the ability to stock and randomly access a large number of substrate carrier pods, or other containers, fixtures, parts, or assemblies used in an automated production process. The system uses a minimal footprint while providing a simple and reliable design that has a low repair time.
Suspending an invert mounted robot from the top of the enclosure provides clearance for the robot to function without obstruction. Floor area is therefore available for other system components and additional area for stored items. A FOUP or SMIF pod cleaner is one example of a process that can be incorporated into the system using this area. Additionally, this configuration provides improved access to the robot for maintenance or replacement.
The seventh axis on the robot, using a swiveling end-effector, allows the robot to capture material at all locations effectively, thus making accessible locations that would otherwise be inaccessible without the additional axis.
The seventh axis can be implemented with a passive or active control. A passive system uses an upper dowel and bearing to permit the pod holder to swing freely, relying on gravity to maintain an upright orientation. An active system uses electrical, pneumatic, or hydraulic mechanisms to maintain the end-effector in the desired orientation.
An automatic teaching capability uses proximity sensors, angle encoders on the robot axes, and torque feedback from the robot motors to allow the robot system to sense locations and obstructions and thereby define the location of features in the storage system and the optimum trajectory for movement between points.
The storage system is suitable for intermediate term stocking and short term buffering of articles. The stored articles can be substrate carriers, for example front opening unified pods (FOUPs), standard mechanical interface (SMIF) pods, or substrates without carriers.
A removable service cart provides access to the interior regions of the system to expedite servicing the system and it subassemblies.
The device comprises a robot including an arm movable in a plurality of degrees of freedom, the arm having a free end. An end effector is connected the robot and has a clasping end mounted to the arm proximal to the free end so as to be positionable by the robot. The robot positions the clasping end of the end effector with respect to the substrate or substrate carrier as to properly position the end effector for pick up of object. The end effector has one degree of freedom to allow greater flexibility for the robot to access storage locations. The robot is mounted inverted to facilitate greater mobility in a small confine without the robot structure interfering with access of storage locations.
The present invention uses a method of stocking/buffering substrate and substrate carriers comprising the following steps:
providing a robot having an arm movable in a plurality of degrees of freedom and an end effector connected with the robot;
automatically moving the arm to align the end effector to pick up or place material in and out of buffer system.
A buffer system constructed and operated in accordance with the present invention enables a system that is completely automatic in operation, has a minimized footprint, operates reliably, and has a rapid repair time.
The buffer system is capable of handling the FOUP or SMIF pods and transferring directly to the process equipment for loading and unloading.